Clinical Application Of Radionuclide Imaging In Idiopathic Dilated Cardiomyopathy

Abstract (Part1):The hypothyroidism may aggravate myocardial injury in patients with idiopathic dilated cardiomyopathy:the evidence based on99mTc-MIBI SPECT/18F-FDG PET imaging and cardiac MRIObjective:Thyroid hormone plays an important role in cardiovascular system and hypothyroidism can aggravate myocardial injure. The purpose of this study is to explore the relationship between hypothyroidism and myocardial injury in patients with idopathic dilated cardiomyopathy (IDCM) by99mTc-MIBI SPECT/18F-FDG PET and late-gadolinium enhancement cardiac resonance imaging (cMRI-LGE).Methods:63consecutive patients (42male and21female,52±11years old) with IDCM at Fu Wai Hospital were enrolled from October2010to December2012. Serum TT3, TT4, FT3, FT4and TSH were measured using a fully automated chemiluminescent immunoassay. All patients underwent99mTc-MIBI myocardial perfusion SPECT/18F-FDG myocardial metabolism PET imaging and cMRI-LGE.17segments model was used for segmental analysis. Patterns of perfusion/metabolism were classified as normal, mismatch, mild-to-moderate match and severe match, and cMRI-LGE was classified into3categories (non-LGE, mid-wall LGE and transmural LGE).Results:All patients were respectively divided into two groups:the euthyroid group (53patients) and the hypothyroidism group (10patients) according to the level of serum thyroid hormone. For99mTc-MIBI SPECT/18F-FDG PET imaging, the percentage of normal perfusion/metabolism segments in the euthyroid group are apparently higher than that in the hypothyroidism group (71.8%vs57.6%, x2=13.5, P<0.001); whereas the percentage of perfusion/metabolism mismatch segments in the euthyroid group are significantly less than that in the hypothyroidism group (17.8%vs31.2%, χ2=16.2, P<0.001). For cMRI-LGE, the euthyroid group had a higher percentage of non-LGE segments than hypothyroidism group (87.4%vs69.4%, x2=35.7, P<0.001), however had a lower percentage of mid-wall LGE segments than hypothyroidism group (4.7%vs24.1%, χ2=74.7, P<0.001). Conclusion:Hypothyroidism does a detrimental effect on myocardium.99mTc-MIBI SPECT/18F-FDG PET imaging is sensitive in detecting viable/ischemia myocardium, and cMRI-LGE is good at detecting moderate fibrosis. Combining SPECT/PET imaging and cMRI-LGE for assessing myocardial injury would provide physicians with more comprehensive information and has potential value for evaluation of therapeutic efficiency using thyroid hormones for patients with IDCM and hypothyroidism. Abstract (Part2):Analysis of the relationship between septal myocardial metabolism and left ventricular mechanical synchronization in patients with idiopathic dilated cardiomyopathy and left bundle branch blockObjective:To explore the relationship between septal myocardial metabolism and left ventricular mechanical synchronization in patients with idiopathic dilated cardiomyopathy (IDCM) and left bundle branch block (LBBB) using gated18F-FDG myocardial metabolic imaging for assessment of18F-FDG uptake in septal myocardium and phase analysis.Methods:20consecutive patients (11male and9female,54±11years old) with IDCM and LBBB were enrolled from October2010to May2013. All patients underwent gated18F-FDG myocardial metabolic imaging. TrueD software was used to determine the maximal standardized uptake value (S-SUVmax) and the average standardized uptake value (S-SUVavg) of septal18F-FDG uptake and the maximal standardized uptake value (L-SUVmax) and the average standardized uptake value (L-SUVavg) of lateral18F-FDG uptake. Bandwidth (BW), standard deviation of bandwidth (SD), left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV) and left ventricular ejection fraction (LVEF) were derived from phase analysis and ventricular functional assessment by QGS software. The relationship between18F-FDG uptake in septal myocardium and left ventricular mechanical synchronization was analyzed by simple linear regression analysis.17segments model was used for segmental analysis. QGS software was used to assess segmental wall motion score.Results:Both septal SUVmax and SUVavg showed significantly negative correlation with BW (r=-0.44, P<0.05and r=-0.48, P<0.05, respectively), and also with SD (r=-0.57, P<0.01and r=-0.51, P<0.05, respectively). However no significant correlation was found between septal SUVmax, SUVavg and LVEDV, LVESV and LVEF (all were P>0.05). The sum score of septal segment wall motion was significantly higher than lateral wall (t=3.12, P<0.01).Conclusion:It is confirmed that significant relationship between decreased septal myocardial metabolism and left ventricular mechanical dyssynchrony in patients with IDCM and LBBB. Gated18F-FDG myocardial metabolic PET imaging could simultaneously evaluate myocardial metabolism and left ventricular mechanical synchronization, and is available for prognostic evaluation and therapy monitor. Abstract (Part3):Relationship between myocardial glucose metabolism in right heart and cardiac function in patients with idiopathic dilated cardiomyopathyObjective:To explore the relationship between myocardial metabolism in right heart and cardiac function in patients with idiopathic dilated cardiomyopathy (IDCM).Methods:64consecutive patients (45male and19female,53±12years old) with IDCM were enrolled from October2010to May2013. All patients underwent18F-FDG myocardial metabolic PET imaging, cardiac MRI and echocardiography. TrueD software was used to determine the18F-FDG average standardized uptake value in right (SUV-RV) and left (SUV-LV) ventricular free wall, and the ratio of SUV-RV and SUV-LV (SUV-R/L). Cardiac MRI was used to evaluate LVEF, RVEF and late-gadolinium enhancement (LGE) in left heart. Pulmonary artery systolic pressure (PASP) was measured by echocardiography.Results:Both SUV-RV and SUV-R/L had significant negative correlation with LVEF (r=-0.48, P<0.001and r=-0.33, P<0.01, respectively) and also with RVEF (r=-0.45, P<0.001and r=-0.44, P<0.001, respectively). There was a significant positive correlation between SUV-R/L and PASP (r=0.58, P<0.01).Conclusions:Our study showed that the myocardial glucose metabolism in right heart closely correlated with left and right ventricular function. The assessment of18F-FDG uptake in right heart by PET imaging was useful for evaluation of severity and prognosis in IDCM patients.